All the dread over the L-Pocalypse — the fear of a 15-month L train shutdown, the planning for alternate routes, the idea of panicked commuters jamming East River ferry boats — is proving way overblown.

Rebuilding of the L train’s busy Hurricane Sandy-damaged East River tunnel officially begins Friday evening, but major repair work on the damaged stretch has been underway for months, the Daily News has learned.

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After a controversial last-minute change of plans pushed by Gov. Cuomo in January, crews will remove less than 1% of the bench walls, which originally were to be entirely removed and replaced.

Before January, the MTA planned to remove enough concrete from 35,000 feet of bench walls, enough to fill 580 large dump trucks.

Now the bench wall portion of the project involves filling just a handful of dump trucks — and the MTA is nearly halfway done with that part of the job.

Instead of ripping out the cables encased in the bench walls, the MTA is installing brackets on the walls to hold new, modern power and communication lines.

Leaving the bench walls largely intact means the MTA only has to shave about three inches of concrete from the face of the structures every 250 feet, where protruding manholes are in place.

There are 96 of those manholes in the tunnel. Over the past three months, crews have shaved back concrete next to 40 of them.

Old electric cables are revealed from the wall inside the L train tunnel on Thursday. (Go Nakamura/for New York Daily News)

That demolition work — which has nothing to do with water damage from the hurricane — expands the tunnel width by a few inches, giving enough space to run trains at slightly faster speeds.

MTA crews have also replaced both sets of tracks in the tunnels, as well as one of two existing pipes that pump out water in the case of another flood. The agency will add two new pipes to make the tunnel slightly more hurricane-proof. Clamps that will hold those pipes are about halfway installed.

The agency has also refined the idea put forth by the deans of the engineering schools at Cornell and Columbia universities to cover the damaged sections of the bench walls with fiber reinforced polymer, or FRP.

The News got a tour Wednesday night of the tunnel, which was damaged in 2012 when it was flooded during Sandy. The L train is to run with reduced service on nights and weekends for at least 15 months beginning Friday to complete repairs — but sources told The News the service cutbacks could last just 12 months given the amount of work that’s already been done.

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A newly-installed fiber reinforced polymer bench wall is seen Thursday in the tunnel. (Go Nakamura/for New York Daily News)

MTA head of capital construction Janno Lieber said that in January, his team experimented with applying wet polymer to the damaged structures, but found it to be too time consuming. His team came up with a better method in February to cover the crumbling sections with FRP segments manufactured in a factory.

Several of those segments have already been put in place. Roughly 7,900 feet of the bench wall will be encased in the material, which is also used on bridges and boats and is said to be impervious to nearly every element except sunlight.

The remaining construction includes the replacement of rail ties, installation of the racked cables on the tunnel walls, and, most significantly, the demolition of a pair of thin, 3,400-foot stretches of concrete above the bench walls called the duct bank.

Those three-inch-thick sections of concrete house long-abandoned ConEd power lines, and were damaged during Hurricane Sandy. The MTA now plans to remove the sections and the cables entirely. They do not need to be replaced.

Series of metal brackets are seen in preparation to install water pump pipes inside the L train tunnel on Thursday. (Go Nakamura/for New York Daily News)

“This is a more surgical solution,” said Mark Roche, one of the heads of the project. He called the new procedure "fine tuned.”

The MTA initially planned to take the same approach to the L train tunnel as it did with the R train’s Montague St. tunnel in 2013, which runs from Whitehall St. in Manhattan to Montague St. in Brooklyn. That shutdown caused 14 months of service disruptions as crews demolished and replaced an entire set of bench walls.

Lieber and Roche were not working at the MTA then. Both believe the MTA and its consultants had planned to take the same approach with the L train simply because the agency had done it before.

Roche previously oversaw construction on the new Tappan Zee Bridge, a rare New York project that came in within budget and on time. He joined the MTA in September 2016.

While the L train work is underway, riders will be offered data showing the amount of potentially dangerous silica dust in the subway tunnel air. The data will be updated weekly.

Roche said the MTA will carry out the remaining demolition work on weekends. Overnight work from Mondays through Thursdays will consist of tasks like pipe and rail tie installation.

Now, the MTA’s biggest challenge is to handle the rush of night and weekend commuters along the L line during reduced service.

MTA workers are seen in the L train 1st Avenue station on Thursday night in Manhattan. (Go Nakamura/for New York Daily News)

L trains will run every 10 minutes within Brooklyn from around 8 p.m. to 5 a.m. each weeknight and throughout the weekends. During the same hours, they’ll run every 20 minutes in Manhattan and across the East River.

The agency has admitted that some trains may be too packed to board while service is reduced, and is hoping riders will switch to other subways and use a new set of free shuttle buses that will shepherd folks between the L, G, J and M lines in Brooklyn.

MTA Chairman Pat Foye called Lieber and Roche “heroes.” “They did an unbelievable job,” he said. “They improved the lives of 250,000 people.”